1. Field of the Invention
Embodiments of the present invention generally relate to apparatus and method for heating a semiconductor processing chamber. Particularly, the present invention relates to a furnace having a multizone heater for heating a semiconductor processing chamber.
2. Description of the Related Art
Some processes during semiconductor processing are performed in a furnace where on or more substrates are processed in an elevated temperature. It is essential to heat the substrate or substrates uniformly, especially in a batch processing, a commonly used process step that can process two or more substrates simultaneously in one region. Batch processing has been proven to be effective in increasing device yield and reducing cost of ownership. A batch processing chamber generally processes a batch of vertically stacked substrates within a chamber volume. Process steps performed in a batch processing chamber, such as atomic layer deposition (ALD) and chemical vapor deposition (CVD), generally require substrates to be heated uniformly. Therefore, a batch processing chamber generally comprises a heating system configured to heat a batch of substrates. However, it is challenging to heat a batch of substrate uniformly and such a heating system may be complicated, difficult to maintain and costly to repair.
FIGS. 1 and 2 illustrate a heated batch processing chamber known in the art. FIG. 1 illustrates a batch processing chamber 100 in a processing condition. In this condition, a batch of substrates 102 supported by a substrate boat 101 is processed in a process volume 103 defined by a top 104, sidewalls 105, and a bottom 106. An aperture 122 formed in the bottom 106 provides a means for the substrate boat to be inserted into the process volume 103 or removed from the process volume 103. A seal plate 107 is provided to seal off the aperture 122 during a process.
Heating structures 110 are generally mounted on exterior surfaces of each of the sidewalls 105. Each of the heating structures 110 contains a plurality of halogen lamps 119 which are used to provide energy to the substrates 102 in the process volume 103 through a quartz window 109 mounted on the sidewall 105. Thermal shield plates 108 mounted on an inside surface of the sidewalls 105 are added to the process volume 103 to diffuse the energy emitted from the heating structures 110 to provide a uniform distribution of heat energy to the substrates 102.
The sidewalls 105 and the top 104 are generally temperature controlled by milled channels 116 (shown in FIG. 2) formed in the sidewalls 105 to avoid unwanted deposition and for safety reasons as well. When the quartz windows 109 are hot and the process volume 103 is under vacuum, undue stress would cause an implosion if the quartz windows 109 were in direct contact with the temperature controlled sidewalls 105. Therefore, O-ring type gaskets 124 (constructed of a suitable material such as, for instance, viton, silicon rubber, or cal-rez graphite fiber) and strip gaskets 123 of a similar suitable material are provided between the quartz windows 109 and sidewalls 105 to ensure that the quartz windows 109 do not come in direct contact with the sidewalls 105. The thermal shield plates 108 are generally mounted on the sidewalls 105 by insulating strips 125 and retaining clamps 126. The thermal shield plates 108 and the insulating strips 125 are made of a suitable high temperature material such as, for instance, graphite or silicon carbide. The retaining clamps 126 are made from suitable high temperature material such as titanium. The milled channels 116 formed in the sidewalls 105 may be temperature controlled by use of a heat exchanging fluid that is continually flowing through the milled channels 116.
The heating structures 110 are further described in U.S. Pat. No. 6,352,593, entitled “Mini-batch Process Chamber” filed Aug. 11, 1997, and U.S. patent application Ser. No. 10/216,079, entitled “High Rate Deposition At Low Pressure In A Small Batch Reactor” filed Aug. 9, 2002 which are incorporated herein by reference.
Referring now to FIG. 2, process gases used in depositing layers on substrates 102 are provided via a gas injection assembly 114. The gas injection assembly 114 is vacuum sealed to the sidewalls 105 via an O-ring 127. An exhaust assembly 115 is disposed on an opposite side of the gas injection assembly 114. The sidewalls 105, the top 104 and the bottom 106 are typically made of metals, such as aluminum.
The batch processing chamber 100 contains complicated system for heating, vacuum seal and thermal isolation. The heating structures 110 are difficult to assemble and service because special fixtures are required for removal and replacement. Furthermore, it would be difficult to control the heating uniformity using the heating structure 110.
Therefore, there is a need for a simplified heating system to heat a batch of substrates uniformly in a semiconductor processing chamber.